Infiniti2000 said:
The purpose of me asking these questions is to show why the implied meaning behind your statement doesn't hold water.
Does that mean that skeleton actually doesn't apply his DR? What kind of damage would a rocky outcropping do? At what point does it go from 'bludgeoning' to 'piercing'? And, although everyone ignored my question, does an adamantine floor overcome DR/adamantine?
1. Sorry, too much CSI. I meant to Say Trauma, not blunt trauma. Any physical damage (slashing, piercing, etc). I sounded like a Police report "And the goblin died by blunt trauma to the head".
2. Falling on an Adamantine Floor would overcome DR/-Adamantine (assuming it was refined Adamantine & not just adamantine infuse ore).
3. My answer does hold water as it is very concave.

Or, I just presented my position very poorly. Here is a better example.
Supposition: A race of Halflings with DR 5/Adamantine (so it’s a Ex as opposed to Su ability).
Say one of these Halflings is climbing up a 500' cliff when he fails his Climb check (horribly) near the top & falls to his doom. At the half-way point he hits an outcropping with a nice rock on it. A good sized rock. A nice flat one like you would use to skip over a pond, if you could pick up a 500 pound rock.
Does the Halfling get to apply his DR 5/Admanatine against the rock he hit? (not as if knocking off 5 really matters at that point).
Now, his dear old grandfather wonders why Bill (I'll call Splat #1 Bill) hasn't returned from his cliff climbing, so he goes to look for him. When he gets to the base of the cliff he spies poor old Bill's flattened remains half-way up the cliff. Unfortunately for Ted (I'll call gramps Ted), as he's looking up at the Bill's final resting place an Earthquake hits, shaking Bill (and his finally resting place down the face of the cliff). Now, Ted rolls a 1 on his Reflex save to get out of the way and Bill's Final Resting Place (the Nice Rock) lands on Ted's head. Then his Shoulders. Then his Torso, then on down to his feet whereupon said Nice Rock finally stops with poor old Ted beneath it.
Does Ted get to apply his DR 5/Adamantine against the Rock that hit him? (Again, not as if knocking 5 points off matters much.
Then, along comes Reinhold the Hill Giant. He notices the Nice Rock (now painted a pretty red on both sides). As really, really Nice Rocks are hard to find (especially pre-coated in gore ones) Reinhold is very happy & looks to try out his new Nice Rock as soon as he can.
Alas, Rob (Bill's Brother) is out searching for Bill & Ted. As family luck would run he rolls a '1' on his Hide check & Reinhold Spots him. Anxious to try out his new Nice Rock, he wings it at poor Rob for a direct hit. In fact, the blow would likely have killed him had it not been for his Damage Reduction 5/Adamantine. Of course, the next round he losses Initiative & the Reinhold does a Charge/Full Power Attack Critical Hit with his Great club and Rob becomes Hill Giant Stew.
So, why did Rob get his DR 5/Adamantine against the VERY SAME NICE ROCK that did in Bill & Ted?
The rules are very clear that the DR works vs a Giant's Thrown Rock. What is so special (actually unspecial) about the Hill Giant once he picks up a rock DR suddenly kicks in?
I've made a point to make this Ex DR as Opposed to Su DR. Su, is after all, Supernatural, and the old, Magic is just plain weird defense kicks in.